1. Field of the Invention
This invention relates to the art of geophone stringing and more particularly to a double-plug seismic connector or takeout clip having a cable adapted to connect a geophone across the male and female contacts in each plug of the connector.
2. Description of the Prior Art
In seismic prospecting, whether on dry lands or marsh and swamp areas, "spread" cables are used to interconnect "strings" of geophones to seismic recording instruments. Each string has one or more single-plug connectors with "leader" cables that connect two or more geophones. The leader cables have T-couplers for making electric junctions therealong. The geophone strings are connected to a connector coupled to a pair of conductor wires in the multi-wire spread cable.
The geophones are electrically interconnected with leader cables at spaced intervals in various networks consisting of series and parallel combinations. The process of interconnecting geophones is commonly referred to as "stringing". The art of geophone stringing has been plagued with numerous problems which are described, for example, in U.S. Pat. No. 3,956,575. This patent relates to a hybrid seismic takeout clip which has exposed takeout contacts.
In one prior art stringing method, single-plug connectors and T-type couplers are used for interconnecting geophones and leader cables. One type of commercially known T-coupler is a completely molded T around the leader cables' junction; another type is a fastened T formed from two members which are clamped together around the junction, and then the inside of the T is filled with a suitable potting compound. Both known T-couplers provide a waterproof junction, but the molded T is impossible to repair in the field because the seismic crew has no injection molding equipment, while the fastened T requires considerable skill and time to first dismantle and remove the potting compound and then to reassemble and to reshoot the compound into the T.
Another type coupler for joining three leader cables is disclosed in said U.S. Pat. No. 3,956,575 which requires no potting compounds. This coupler is still labor-intensive and is also prone to human error. Such errors are normally not detected until final checkout is made on the assembled geophone strings. When a defective geophone string is found, it is very time-consuming to locate the origin of the trouble which frequently lies in erroneous inter-wire connections.
In addition to the problems encountered while stringing the geophones in the place of manufacture of the geophones and the geophone strings, problems also exist in the field while using the geophone strings. Thus, T-couplers become frequently damaged by physical objects and their outer jackets and housings may be eaten up by rodents, or they become damaged by rough handling. If trouble shooting is very time-consuming or costly, sometimes a very expensive entire geophone string may have to be discarded because the fault cannot be easily located and may lie in a T-coupler.
It is a main object of the present invention to overcome the above-mentioned drawbacks of the known geophone stringing art and to provide a method and means for stringing geophones without the use of couplers. The invention reduces considerably the amount of labor required and hence the cost of stringing geophones.
It is a further object of the present invention to reduce, as much as possible, the possibility of human error in the assembly and the subsequent trouble shooting of the geophone strings.